The present invention relates to technology to control an internal combustion engine, based on a new air intake amount, which is equipped with a variable valve operating apparatus for changing opening and closing characteristics of intake and exhaust valves.
There has been known an electronic controlled fuel injection apparatus called as a speed density type which determines a basic fuel injection quantity based on an engine intake pressure and an engine rotation speed (see Japanese Unexamined Patent Publication No. 58-206624).
Further, there has been known a variable valve operating apparatus which changes opening and closing characteristics of intake and exhaust valves, such as opening and closing timing, a lift amount, an operating angle.
In a variable valve operating apparatus disclosed in Japanese Unexamined Patent Publication No. 10-068306, the opening and closing timing of a valve is advanced or retarded by changing a phase of a camshaft relative to a crankshaft.
In the above electronic controlled fuel injection apparatus of speed density type, the intake pressure is detected as the sum of a new air component pressure and a cylinder residual gas pressure.
Here, in an engine equipped with a variable valve operating apparatus, a cylinder residual gas pressure is changed with a change in opening and closing characteristics of intake and exhaust valves.
As a result, even though the intake pressure is the same, a new air component pressure is changed depending on an operating state of the variable valve operating apparatus. Accordingly, if combining the electronic controlled fuel injection apparatus of speed density type with the engine equipped with the variable valve operating apparatus, then a fuel injection quantity to be calculated based on the intake pressure does not correspond to a new intake air amount, causing a problem in that an air-fuel ratio deviates from a target value.
The present invention has an object of enabling to accurately detect a new air component pressure (namely, new air intake ratio) even though opening and closing characteristics of intake and exhaust valves are changed, to improve control accuracy of a fuel injection quantity and the like.
To achieve the above object, according to the present invention, the construction is such that, in an internal combustion engine equipped with a variable valve operating apparatus to change opening and closing characteristics of intake and exhaust valves, a new air intake ratio of the engine is calculated based on an intake pressure of the engine, a rotation speed of the engine, and the opening and closing characteristics of the opening and closing valves adjusted by the variable valve operating apparatus, to calculate engine operation factors such as a fuel injection quantity, an ignition timing and the like based on the calculated new air intake ratio.
The other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.